How Birds Get Around

Now that the magnetic pole reversal is in progress, somebirds are having trouble migrating and are ending up in thewrong places. They’re also leaving at the wrong time,because global warming is giving them false signals. It’sbecome important for scientists to understand how birdsnavigate.

Amanda Onion writes on abcnews.com that how migrating birdsfly for hundreds or even thousands of miles, often at night,to end up in the same spot year after year has baffledbiologists for years. Some birds orient themselves using thesun or Earth’s magnetic field, while others use landmarks onthe ground or even familiar smells.

Biologist Henrik Mouritsen says, “How they get theirmagnetic sense is the last question that was left to beunderstood. Now we’re pretty close.” To learn how birdsfunction, Mouritsen decided to intentionally confuse them.They captured songbirds in Illinois and Iowa as they madetheir journeys north in the spring and exposed them to afalse magnetic field at dusk, then released them. The birdstook off in the wrong direction, but by the second night,they had managed to correct themselves and pointed northonce more.

This suggests that the birds use the setting sun to correcttheir internal compasses. This should help them compensatefor the shifting magnetic field.

In the United States, there are four main bird routes: theAtlantic, Mississippi, Central and Pacific flyways. Forbirds that have flown the same route before, there’sevidence that they use landmarks below them to find their way.

Hans-Peter Lipp used Velcro to attach lightweight GPSlogging devices on the backs of homing pigeons, whichrevealed that the birds liked to travel above highways.Sometimes they even waited to see an highway exit beforemaking a turn. Lipp says, “It’s like the way a pilot of asmall airplane may prefer to follow a road or powerlinecoincident with the compass rather than watching only thecompass in the cockpit.”

Scientists are still trying to learn how birds’ internalcompasses work. Physicists thought migrating birds may carrya protein in their eyes that is activated by blue and greenlight. When activated by this light (which is available bothnight and day), the proteins would become sensitive toEarth’s magnetic field.

Mouritsen dissected some garden warblers and located theproteins in the retinas of the birds, which had just beenexposed to the blue green light and to a magnetic field. Hefound the proteins had been altered according to the changein the magnetic field and had sent this information to thebirds’ brains. The birds see Earth’s magnetic fieldsuperimposed over their normal vision. Mouritsen says,”Imagine a light spot with concentric darker rings around itthat moves around in the retina depending on where you look.This is what the bird sees.”

Native Americans know a lot about thesecretsof the sky.

Photo Credit: http://www.freeimages.co.uk/

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